How to call vertex groups in Animation nodes [SOLVED]
You can achieve that effect by controlling the scale of the normals with the vertex weight.


First, instanced an object (Cone) on the vertex locations of the base object (Cube) using this node-tree:

Then, remap the weight (using Vertex Weight Input node) which is in range (0, 1) to (1, -1) using Map Range node with the Threshold (in Threshold node) = 0.5 i.e., vertices which have weight less than 0.5 will have normals with scale = 1 (+ve direction) and vertices which have weight equal or greater than 0.5 will have normals with scale = -1 (-ve direction).



You can very the Threshold as you like.

Blend File: